Hi all, On Fri, Jan 27, 2012 at 7:33 PM, Tom Rini <tom.r...@gmail.com> wrote: > So, what do we want to do here? We really want to get this fix in so > we can get the hawkboard SPL changes in, and the other platforms / > fixups that are gated by that. > > If I can sum it up, in the relevant section of code we have incorrect > comments and the init code is not following what the manual says the > correct sequence is. However, given the (potentially wide) impact the > changes would have, Albert had previously requested making the change > opt-in (but I believe this request came before the "the manual says we > must do ..."). If this is still the case? If so, can we get an > updated patch? Thanks!
A few thoughts: 1) Before commit ca4b55800ed74207c35271bf7335a092d4955416 the low level initialization code that we are discussing here was only executed if CONFIG_SKIP_LOWLEVEL_INIT is not defined. For ARM926EJS the relevant section in start.S looked like this #ifndef CONFIG_SKIP_LOWLEVEL_INIT flush caches turn off dcache, do some other configurations of the CPU, enable icache call the SoC specific lowlevel_init #endif For DA850 SoCs we had no lowlevel_init routine and therefore CONFIG_SKIP_LOWLEVEL_INIT defined in all board configurations. The lowlevel initialization was done by TI's UBL boot loader. Now we have boards that don't use UBL (e.g. enbw_cmc, calimain, da850evm when used with the SPL), therefore we need some lowlevel init. Most important configuration is enabling icache, otherwise u-boot startup gets really slow. Since commit ca4b55800ed74207c35271bf7335a092d4955416 it is flush caches turn off dcache, do some other configurations of the CPU, enable icache #ifndef CONFIG_SKIP_LOWLEVEL_INIT call the SoC specific lowlevel_init #endif So the change that has a big impact is already done and in mainline. Perhaps we should revert that change and instead remove CONFIG_SKIP_LOWLEVEL_INIT from the da850 board config files. But since we don't need the lowlevel_init function for DA850 SoCs we must either add a dummy function or add some additional defines that allow removing the CONFIG_SKIP_LOWLEVEL_INIT define without calling lowlevel_init. Any suggestions how such defines should be called or how the logic behind them should be so it doesn't cause breakage of existing boards? What do you think? Or is reverting to dangerous since we would change the behavior of start.S twice if we do so? 2) The current version of Sughosh's patch does not change the logic behind the LOWLEVEL_INIT defines but just fixes the code to agree with ARM's manual. Instead of invalidating the cache it now is flushed. I think we should therefore merge his patch (@Tom: Yes, the manual says we must do.). The big change that Albert fears was already done earlier in commit ca4b55800ed74207c35271bf7335a092d4955416. And while we are doing this we also get the comments right. 3) As Sughosh pointed out, the current code changes the V bit (location of exceptions). Sughosh's patch removes this code that does this change. I'm not sure if this is correct or not, so maybe you, Tom, could put your TI hat on again and clarify this? 4) The current code turns on icache. This is great since my board executes u-boot directly from flash until it relocates itself and thus the startup time is greatly reduced by using icache. However, there is this CONFIG_SYS_ICACHE_OFF define. Should the code be changed to respect this define? Regards, Christian _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
